Anatomy: Face, Scalp, Parotid gland Flashcards
5 layers of skin?
S: skin
C: CT - dense - contains vessels and nn.
A: aponeurosis epicranius
L: loose CT - usually this is plane during scalp injury
P: pericranium (periosteum, outer CT of flat bones of skull)
why do scalps bleed so much?
scalp is highly vascular and because the vessels are embedded within the dense ct of layer 2 there is limited constriction when lacerated. There are many anastomoses as well, and there is no single vessel to compress to stop the bleeding.
how is scalp innervated?
spinal nerves posterior portion of head
trigeminal n. anterior portion of head
what are spinal nn. innervating scalp?
greater occipital: straight middle back of head
C3: inferior posterior scalp
Lesser occipital: behind ear
great auricular: underneath ear
what cranial nn. innervate scalp?
Trigeminal branches:
auriculotemporal of V3 (in front of ear and up)
zygomaticotemporal V2 (temple and up)
supraorbital V1 (forehead and above eyes)
supratrochlear branch of V1 (nose/midline forehead)
what is the arterial supply of the scalp?
from external carotid a: occipital, posterior auricular, superficial temporal
from internal carotid a: supraorbital a, supratrochlear a.
how does scalp drain?
vena comitantes of aa. emissary vv (drain through bones of skull to dural venous sinuses)
why are scalp infections potentially dangerous?
scalp infection/bleeding can spread easily within the loose connective tissue layer (layer 4); can spread within the eyelids and dorsum of the nose and cause “ecchymosis” (extravasation of blood under skin).
how are facial expression muscles innervated?
SVE portion of facial n.
- all are derived from pharyngeal arch 2
orbicularis oculi
muscles associated with eyes/eyebrows
- orbital part: surrounds orbit and forcefully closes eye
palpebral portion: within eyelid to gently close eye
lacrimal portion: within medial corner of eye, helps with lacrimal fluid drainage
corrugator supercilli
draws eyebrows down and in - worried look
occipitofrontalis
muscles associated with scalp and forehead
- frontal belly: elevates eyebrows, wrinkles skin of forehead
- occipital belly- retract scalp, helps with “suprised” expression
orbicularis oris
closes lips/mouth
buccinator
keeps cheeks in contact with gums to food does not accumulate in vestibule of mouthg
levator labii superioris
elevates upper lip
levator anguli oris
elevates upper lip; widens mouth
zygomaticus major
elevates upper lip “main smile muscle”
zygomaticus minor
elevates upper lip
risorius
stretches lips laterally into wide muscle
levator labii superioris alaeque nasi
elevates upper lip and flares nostrils
depressor anguli oris
depresses lower lip; frown
depressor labii inferioris
depresses lower lip; pout/frown
mentalis
protrudes lower lip: pout mm.
procerus
wrinkles skin over dorsum of nose
nasalis
flares nostrils
platysma
depresses mandible, tenses skin of lower face and neck
where does facial nerve travel?
exits brainstem and enters internal acoustic meatus. courses laterally between cochlea and semicircular canals and along posterior wall of middle ear, exits facial canal via stylomastoid foramen
branches of facial nerve?
- posterior auricular n. - supplies occipital belly of occipitofrontalis
- digastric n.
- stylohyoid n.
- temporofacial trunk:
- temporal branch (above eye),
- zygomatic branch (side of eye/upper cheek)
- buccal branch (to nose/mouth) - cervicofacial trunk:
- buccal branches (transversely across face)
- marginal mandibular branches (lower mandible border)
- cervical branch (to platysma )
Bell’s Palsy
= facial n. paralysis
- many cases are idiopathic; although linked to herpes virus, trauma or lesion along course of nerve
- results in paralysis of facial expression
- facial asymmetry and drooping
- drooping of lower eyelid causes drainage of tears and ulceration of eye
- paralysis of orbicularis oris causes dribbling of saliva from mouth
- loss of buccinator = food accumulation within cheek and teeth
- impaired speech
What does V1 supply?
opthalmic nerve
- skin of forehead, upper eyelid, nose
- branches: supratrochlear n. supraorbital n, lacrimal n, infratrochlear n, external nasal n.
What does V2 supply?
Maxillary n.
- provides skin of temporal region, upper cheek and lip, lower eye lid, ala of nose
Branches: zygomaticotemporal, zygomaticofacial, infraorbital n.
what does V3 supply?
mandibular nerve
- lower cheek, lower lip, chin
- provides: auriculotemporal n, buccal n, mental n.
trigeminal neuralgia
a neurological condition characterized by episodes of brief, intense facial pain over an area of CN V distribution.
- cause believed to be demyleination of axons within the sensory root of CNV. some cases can be due to compression by the superior cerebellar a.
- divisions affected: V2>V3>V1
nerve block administration?
- infraorbital n: injected around infraorbital foramen
- mental n: injected around the mental foramen on chin
- buccal n: injected via the oral vestibule just posterior to the 3rd mandibular molar
hepres zoster
often affects the trigeminal ganglion
- due to reactivation of previous infection of dorsal root or sensory ganglion by varicella zoster virus
- rash confined to one dermatome
- most often affects V1 and can lead to scarring/ulceration of cornea
facial artery?
- facial artery: branches from external carotid, through submandibular gland, arches over mandible just anterior to masseter to enter face. takes tortuous course along angle of mouth to lateral side of nose/medial eye angle (gives off: inferior and superior lalbial branches, lateral nasal and angular a.)
superficial temporal artery?
terminal brnch of external carotid a.
- gives off transverse facial a, frontal branches and parietal branches.
maxillary a?
branch off of external carotid a.
- gives infraorbital a, buccal a, and mental a.
opthalmic a.
branch of internal carotid a. - gives off: supraorbital supratrochlear middle palpebral lacrimal dorsal nasal a.
retromandibular vein
formed from union of superficial temporal and maxillary vv.
- divides ant/post division
- anterior division merges with facial v.
- posterior division merges with posterior auricular v. to form the external jugular v.
facial v.
begins at medial corner of eye as angular v.
- joins anterior division of retromandibular v. to make common facial v. which then drains to IJV
- communicates with deeper plexuses: with pterygoid plexus via deep facial v, with cavernous sinus via opthalmic vv.
infection from face
the central face area is a “danger area” for infection to travel into the skull or deep face b/c the facial v. anastamoses with pterygoid plexus and cavernous sinus
lymphatic drainage
- lymph drains to submental, submandibular, parotid lymph nodes
- all ultimately flow to deep cervical lymph nodes along internal jugular v.
where does parotid duct exist?
- leaves anterior border of gland and crosses the masseter muscle - pierces buccinator muscle and mucosa of cheek to enter the oral cavity opposite the 2nd upper molar tooth
- abcesses or infections of dental origin may spread to the parotid gland via the parotid duct
what are important structures embedded within the parotid gland?
- facial n.
- retromandibular v.
- external carotid a.
- during parotidectomy these structures must be isolated and protected in order to preent damage.
what are chief complaints of problems with the parotid gland?
eyes dry and red
dry mouth
eyes are droopy
Parasympathetic innervation of parotid gland?
Preganglionic: glossopharyngeal nerve with cell bodies located in salivatory nucleus in brain stem
- CN IX exits at jugular foramen and gives a tympanic branch, the tympanic n. then enters the middle ear via tympanic canaliculuous. Travels through the middle ear and transforms into lesser petrosal n. Lesser petrosal n.
- Lesser petrosal n. in the middle cranial fossa exits via the foramen ovale, once in the infratempora fossa it synapses in otic ganglion.
Postganglionic: Cell bodies are located in otic ganglion. Postganglionic fibers travel with auriculotemporal branch of V3
Function: stimulates grand secretion from parotid gland
sympathetic innervation to parotid gland
preganglionic cell bodies located in spinal cord at levels T1-4
Postganglionic cell bodies in superior cervical symp. ganglion
- postganglionic fibers travel with external carotid n. to parotid tissue
function: vasomotor: alters type of secretion
Parotiditis
inflammation of the parotid gland
- painful due to stretching of parotid sheath
- pain can be carried via V3 and great auricular n.
- often pain will “refer” to auricle, TMJ and external acoustic meatus
sialolith
calcified concretion that can sometimes form in the parotid gland
if it passes into the parotid duct the duct can become blocked and it is quite painful
